A new series of fused indazole derivatives: solid state synthesis; antibacterial and antifungal activities

Novel 4,6-diaryl-4,5-dihydro-3-hydroxy-2[H]-indazoles 9 – 16 and 4,6-diaryl-4,5-dihydro-2-phenyl-2Hindazol-3-ols 17 – 24 are effectively synthesized by a solid-state reaction procedure in the presence of NaHSO4 ⋅ SiO2 catalyst under microwave irradiation. All the synthesized compounds are characterized by melting point, elemental analysis, MS, FT-IR, one-dimensional NMR (1H and 13C), D2O exchanged 1H NMR, and two-dimensional HSQC spectroscopic technique. An in vitro antibacterial activity study is carried out against clinically isolated bacterial strains, namely Bacillus subtilis and Micrococcus luteus, and antifungal activity against clinically isolated fungal strains, namely Aspergillus niger, Candida albicans, Candida 6, and Candida 51. Structure-activity relationship results for these 16 compounds have shown that all the compounds 9–24 exerted excellent antibacterial activity. Compounds having electron-withdrawing functional groups 11, 12, 14, 16, 19, 20, 22, and 24 recorded outstanding antifungal activity. The obtained results may be used as a key step for the building of new chemical compounds with interesting antimicrobial profiles comparable to that of the standard drugs.